The field of the invention is flexible casings for optical fiber ribbons and methods for providing such flexible casings and fiber optic cable assemblies incorporating such flexible casings.
Cable assemblies typically include cables and connectors or other hardware joined to the cables. Protection of some kind is usually provided for the portion of the optical fibers or optical fiber ribbons branched from the cable to the connector or connectors. Tubing or the like provides such protection. The tubing may be needed in the manufacture of cable assemblies or in post-installation network adjustments to accomodate future demands on the network. A device, sometimes called a furcation, is often used to protect the joint between the cable and the tubing.
A prior art rectangular tubing for optical fiber ribbons comprises an inner rectangular tube of polyester material which is surrounded by a layer of loose, flexible aramid fibers and an outer rectangular jacket of polyvinyl chloride material. The inner tube has inner surface dimensions of 0.6 mm in height and 3.2 mm in width and outer surface dimensions of 1.5 mm in height and 3.6 mm in width. The outer tube has outer surface dimensions of 2.5 mm in height and 4.9 mm in width.
To make a cable assembly, the prior art rectangular tubing has been provided over a single optical fiber ribbon. The frictional resistance between the material forming the optical fiber ribbon common coating and the inner rectangular tube of the prior art tubing is such that pushing the ribbon through the inner tube by hand has been impracticable over distances more than a few inches. Therefore, a pulling wire has been attached by adhesive to an end of the ribbon to be inserted and the wire has been pulled by hand, thereby pulling the ribbon through the bore of the inner tube. The time necessary to attach and remove the pulling wire must be allowed for in the prior art method. Further difficulties have been experienced due to the detachment of the pulling wire or breakage or other damage to optical fiber ribbons during the pulling process.